Thermostatic air control attachment for oil burners



March 22, 1949. J. w. SCHULZ 2,465,125

' THERMOSTATIC AIR CONTROL ATTACHMENT FOR OIL BURNERS Filed Aug. 4, 1945 INVENTOR. fa/7W M 50/012 WrraP/vn Patented Mar. 22, 1949 UNITED STATES M PATENT OFFICE THERMOSTATIC AIR CONTROL ATTACH- MENT FOR OIL BURNERS John W. Schulz, Bay Shore, N. Y.

Application August 4, 1945, Serial No. 08,866

, 4 Claims. 1

This invention relates to improvements in automatic oil burners, and relates more particularly to novel means for giving the flame relatively more air, compared to the oil supplied, during the first few minutes of operation of an on-ofi oil burner than is given the flame later. The effect is to have an oil burner produce CO2 readings, obtained in the customary manner by analyzing the flue gases, which are relatively low during the first few minutes of burner operation, and which are higher later during the normal operation of the burner.

This arrangement gives a number of important advantages including a reduction in fuel con-. sumption. The flue gas loss is reduced by decreasing the relative air flow to the flame after the burner has operated several minutes. On starting with the burner equipment and boiler or furnace cold, the CO2 content of the flue gases may be, roughly, 8%, whereas after several minutes of burner operation the 002 may be in the range of 10% to 12 /z% which gives maximum efficiency for normal, warm operation, but which frequently is impractical for starting cold.

Another advantage resides in cleaner burning and formation of less smoke and soot. During cold starts, when it has greatest tendencies to form smoke and soot, the flame automatically receives relatively more air and therefore burns with less smoking and sooting than it would otherwise. In addition, this gives smoother starting of the burner. The use of relatively more air for starting tends to eliminate the trouble of starting pulsation which frequently is experienced with on-off oil burners.

The device of the present invention also eliminates the need for seasonal oil burner adjustments. For short on periods in spring and fall when it runs but a few hours total time each day, the oil burner automatically gives the flame more air than for longer, more frequent on periods during the middle of the winter. This eliminates the need for a service man to adjust the air damper of the burner several times a year to make sure of clean burning when the burner operates but a few hours a day, and maximum fuel economy when it runs many hours a day.

After several minutes of operation following a I cold start, an oil burner has reduced tendency to .50

form smoke and soot. When cold or nearly cold, the metal and refractory surfaces near the oil flame take from it more conducted and radiantheat than they do later when heated. They chill the flame and tend to cause formation of smoke and soot. Also, with the heating plant and chimney cold or nearly cold, the chimney draft and. over-fire draft are lower than later during the oil burner on period, and this tends to give the flame less air and to increase formation. of smoke and soot. A pressure atomizing oil burner nozzle,

when cold than when heated after several minutes of burner operation; thus, it tends to cause more smoking and sooting when a burner first operates than later.

Reducing the amount of smoke and soot formed the first few minutes a burner operates saves considerable oil by reducing heat losses due to the escape of oil vapor. This is important during cool operation of the burner, the loss being caused by incomplete combustion and the escape of combustibles from the flame.

Prior to the present invention, it has been the usual practice to adjust a conventional on-oif oil burner so that it would not produce excessive smoke and soot when starting cold. This resulted in excessive loss of heat up the chimney (low CO2 of the flue gases) for the normal, heated operation of the burner. If the burner was adjusted for emcient operation and high CO; during normal, heated operation, the result was formation of excessive smoke and soot for the first few minutes the burner operated after a usual "off period. Also, it resulted in the need to clean. soot from the flues frequently, in higher stack temperatures caused by soot on heating surfaces of the boiler or furnace, and in inefficiency the first few minutes of burner operationbecause of the escape of combustibles from the flame.

The present invention provides an automatic means for feeding the flame relatively more air for starting, and for automatically reducing the air-flow to the flame after the burner has operated for several minutes. This gives cleaner burning and higher combustion efficiency for starting and for short on periods, even while it gives the maximum efficiency practical for the normal, heated operation of the oil burner equipment. It provides means for obtaining more practical and more economical oil-air adjust- For 1 viding a supplemental air damper or other device to give the flame more air automatically when 1 desired. The operation of this air damper is independent of the conventional air damper on the burner, which latter is adjusted by the service man to a fixed position. The supplemental damper is automatic in opening and closing, and is so controlled as to be fully open when the burner equipment is relatively cold following, for example, an idle period for the oil burner of more than, say, eight hours. At the end of a relatively short off period, the automatic air damper will 3 be partly open because, for a relatively warm start, the flame does not need the full extra amount of air for starting. After three or four minutes of'burner operation from a'. cold start, and a slightly shorter period from a warm start;

depending on how warm the burner equipment. and firebox are for starting, the automatic air' Within'a period-of" from 15 seconds to three minutes, depending 'on.

damper will start to close.

the characteristics of the equipment and installation and on the adjustments used, the automatic lowing such cold start, may be adjustable on theinstallation to match characteristics of slow-heating and rapid-heatin installations. Depending on how long it takes to re-set to its coldpositionfi the automatic damper may or may not start to goto. or reach, its fully-open positionduring a very short oil burner off period.

This invention is applicable'to any oil burner which starts and stops automatically, or which gives different flame sizes automatically, and which benefits by feeding the flame relatively more air (comparedto oil) at times of starting or low load thanfor normal operation. This includes atomizinq andvaporizing-type oil burners of the natural-draft, forced-draft, and induced-'' draft types.

In the drawings:

Fig. 1 is a perspective view of a conventional type of forced-draft oil burner'showing one embodiment of the present invention attached thereto.

Fig. 2 illustrates how a' damper of'the present invention may be associated with theoutput side of the blower.

Fig. 3 is a longitudinal section showin onemeans for actuating the damper.

Fig. 4 is a broken end elevation'of the structure" shown in Fig. 3.

Fig. 1 is a schematic showing of one embodiment of the present invention wherein the extraair for the initial period of operation is supplied at the input side of the burner. There is illustrated in Fig. 1 a conventional forced-draft oil" burner HJ having the usual gun tube II and base [2. A fuel nozzle 1 ismounted at the'forward end' ofthe'guntube and the eiTective area of the open end of such tube is reduced by the usual cone or insert 8. A fuel line 9 supplies-oil to the nozzle '1? The blower (not'shownl is driven by motor 13,

an'd'a housing extension In is provided with theusual openings [S'spaced about the outerperiph ery thereof. A circular damper l6 having open:-

ings H is carried by housing extension I4, and

such damper maybe rotated'to an adjusted fixed position to admit a desired quantity of air to'the input side of the blowerfor normal burn'er"oper-- at ion.

It was earlier pointed out that an important ad vantage of the present invention resides in the fact that it may be readily adapted and secured t'oconventional oil burners of virtually any type.

In the instance shown, the end wall l9 of housing extension I4 is provided with a small circular openingy20, and a small damper 2| is mounted within such opening on a: shaft 22 which is journalled in bearings 23. Whereas the diameter of damper 2| may vary, it has been found for most domestic systems that such damper may have a diameterrof :aboutan inch and a half, and opening .20 may be only slightly larger. It will be noted that damper 2| is of the balanced type which does not tug upon its shaft when subject to pressure difference. Acrank 24 is carried at one end of the shaft, such crank being connected as by a link'25 'to another crank 26 carried on a shaft 21 which is rotated by the-mechanism shown in detail in Fig. 3, which will now be described; and which is designated generally by the reference numeral'30.

A mounting block 32 may be secured as by means-of screws 33'to support 34 which may be suitably mounted"relativeto the burner in substantially the position shownin Fig. 1. Block 32 isfprovided with a substantially centrally-disposed aperture 31which forms-a hearing for shaft 21'. At 38"there"is'-shown a conventional bi-metallic helix; such helix-being mounted at its right-hand end on a support 39 carried by block'32. At the opposite end, thehelixis secured, as at 10, to one terminal of' shaft 2']. A tube l3 of insulating material, such as porcelain, is mounted concentrically ofblock 32; and on itsexternal periphery there is wound a number of turns of electric re sistance wire 44. Adjacent the opposite end of theshaft a collar 51 is mounted, as by means of setscrew 48.

When the shaft-is turned due to the transfer of heat from coil 44" to the bi metallic helix, lever 26' likewise turnsby virtue of a slip-clutch arrangement which may comprise a collar seouredto the shaft, a spring 5| carried concentrically thereof, and a second collar 52 which is movable longitudinally of the shaft but is keyed to rotate therewith by means of a suitable key (not-shown) passing into spline 53. Accordingly,

;' spring 5| urges collar 52 against the lever 26.

This arrangement gives the sensitivity desired inasmuch as the helix may make a full revolution during a cycle of operation, although the parts may be'arranged so that the damper may open or close in about one-eighth of a turn. This arrangement also acts as a tension release on the lat-metallic helix.

Resistance coil 44 may be wired in parallel with the motor circuit, or may be included in a supplemental'circuit which is closed when the motor circuit'is closed. For instance, a step-down transformer may be'included in the'burner motor circuit, and the secondary of the transformer connected with the heating coil. The heating of the go" coil raises the-temperature of helix 38, causing it'tostart turning; The construction may be such thatshaftt-fl starts turning in any desired length of. time from a relativelycold'start. This period mayvaryjrom 30'seconds to 5 minutes. rbe' desiredi'to' provide adjustable stops 56 which limit'rotative movement of crank 26. Also, for purposes ,ofadjustment, such lever may be provided with a plurality of holes 51 through any one of'which' a pin may pass for the purpose of connecting thecrank with lever 25.

The'heating element and helix of Fig. 3 may be enclosed in a cylindrical housing 59 having heatinsulating material 60 on the outer or inner sur face thereof. In Fig. 1, air was regulated at the input side of the blower, whereas in the arrange- It mayment of Fig, 2 the air is regulated to the output side. In this arrangement, the housing 62 encloses the blower element 53, and a conventional damper 64 may be rotated to an adjusted, fixed position to permit a predetermined quantity of air to pass into the gun tube 65. In this arrangement, housing 52 is provided with a by-pass tube 66 having damper 67 mounted therein on shaft 68, the shaft having crank 69. The means for rotating shaft 58 may be similar to that shown in Fig. 3. When current no longer flows through the coil 44 due to the burner having stopped operation, lever 26 goes back to its initial position, thus opening damper 2| or 61. This return movement is by design a slow action.

The operation of the device is as follows. During burner operation the heating coil for the bi-metallic element is actuated, thus heating the element and producing rotat on of the damper shaft. It was pointed out that shaft 21 is arranged to rotate over a larger arc than is necessary to move the damper from full open to full closed position. As soon as lever 26 contacts one of the stops, during either the heating period or the cooling period, the shaft 2! is nevertheless permitted to continue its rotation so long as it is driven by the bi-metallic element. This is the function of the friction clutch.

While one form or embodiment of the invention has been shown and described herein for illustrative purposes, and the construction and arrangement incidental to one specific application thereof has been disclosed and discussed in detail, it is to be understood that the invention is limited neither to the mere details or relative arrangement of parts, nor to its specific embodiment shown herein, but that extensive deviations from the illustrated form or embodiment of the invention may be made without departing from the principles thereof as defined by the following claims.

What I claim is:

1. In an oil burner including a burner nozzle, means for delivering air under pressure to the burner nozzle, and a housing therefor provided with a port for admitting air into the housing, the combination of means for increasing the effective area of the port during the initial burning period to admit a relatively greater quantity of air during such period, and for reducing said area to normal size after the burner has reached a normal operating temperature, such means comprising a damper and stops limiting movement thereof in open and closed positions, a shaft upon which the damper is mounted, a helical, bi-metallic element for producing rotation of the shaft to close the damper upon being heated and open the same upon cooling, heating means for the element arranged to be actuated only during operation of the burner, such bimetallic element being arranged to produce rotation of the damper shaft over an are which is greater than is necessary to move the damper from open to closed position, and a friction clutch disposed between the rotation producing means and the damper to permit such added rotation after movement of the damper has been restrained due to action of one of the stops.

2. In an oil burner including a burner nozzle, means for delivering air under pressure to the burner nozzle, and a housing therefor provided with a port for admitting air into the housing, the combination of means for increasing the effective area of the port during the initial burnin period to admit a relatively greater quantity of air during such period, and for reducing said area to normal size after a period of burner operation, such means comprising a damper for the port and stops limiting movement thereof in open and closed positions, a shaft upon which the damper is mounted, a friction clutch connection between the shaft and the damper to permit rotation of the shaft after rotation of the damper is restrained by one of said stops, a helical, bi-metallic element for producing rotation of the shaft to close the damper upon being heated and open the same upon cooling, and heating means for the element arranged to be actuated only during operation of the burner.

3. In an oil burner including a burner nozzle, means for delivering air under pressure to the burner nozzle, and a housing therefor provided with a port for admitting air into the housing, the combination of means for increasing the effective area of the port during the initial burning period to admit a relatively greater quantity of air during such period, and for reducing said area to normal size after a period of burner operation, such means comprising a damper, a shaft on which the damper is mounted, a second shaft, a helical, bi-metallic element for producing rotation of the second shaft, a lever mounted on the second shaft, stops limiting movement of the lever to open and closed positions of the damper, means connecting the lever with the damper shaft, a friction clutch connection between the second shaft and the lever to permit rotation of such shaft after rotation of the lever is restrained by one of said stops, and heating means for the bi-metallic element arranged to be actuated only during operation of the burner.

4. In an oil burner including a burner nozzle, means for delivering air under pressure to the burner nozzle, and a housing therefor rovided with a port for admitting air into the housing, the combination of means for increasing the efiective area of the port during the initial burning period to admit a relatively greater quantity of air during such period, and for reducing said area to normal size after a period of burner operation, such means comprising a damper and stops limiting movement thereof in open and closed positions, a shaft upon which the damper is mounted, a bi-metallic element for producing rotation of the shaft to close the damper upon being heated and open the same upon cooling, a friction clutch disposed between the rotation producing means and the damper shaft to permit movement of such latter means after rotation of the damper has been restrained by one of said stops, and heating means for the element arranged to be actuated only during operation of the burner.

JOHN W. SCHULZ.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,629,253 Breeze May 17, 1927 1,693,060 Smith Nov. 27, 1928 2,012,037 Drew Aug. 20, 1935 2,067.446 Good Jan. 12, 1937 2,224,705 Stringer Dec. 10, 1940 2,227,195 Moule Dec. 31, 1940 

